Variable speed means for variable pitch propeller systems



April 3, 1945-, A. e. FORSYTH ET AL 2,372,667

VARIABLE SPEED MEANS FOR VARIABLE PITCH PROFELLER SYSTEMS Filed April 2, 1943 3 Sheets-Sheet l April 1945. A, G. FORSYTH ET AL 2,372,567

VARIABLE SPEED MEANS FOR VARIABLE PITCH PROPELLER SYSTEMS Filed April 2, 1943 s Sheets-Sheet 2 April 3, 1945. A. G. FORSYTH ET AL 2,372,667

VARIABLE SPEED MEANS FOR VARIABLE PITCH PROPELLER SYSTEMS Filed April '2, 1943 3 Sheets-Sheet 3 those of the selfcontained type.

Patented Apr. 3, 1945 VARIABLE SPEED MEANS FOR VARIABLE PITCH PROPELLER SYSTEMS Archibald Graham Forsyth and George James Smith-Port, Cheam, England, assignors to The Fairey Aviation Company Limited, Hayes, Middlesex, England Application April 2, 1943, Serial No. 481,624

2 Claims.- ('01. 170163) This invention relates to improvements in variable pitch propeller systems for aircraft and more particularly the invention relates to means for effecting pitch changing movements in each direction at different speeds.

The invention, while adaptable for use with variou types of variable pitch propeller systems is especially suited to the type of systems illustrated and disclosed in a copending application of Archibald G. Forsyth, S. N. 449,123, filed June 30, 1942. That application discloses a system in which the pitch changing movement is effected electrically by means of a motor, the circuit in which said motor is connected including cam means for shutting off the motor when the desired pitch position has been effected. However, the speed of pitch change in both direction is the same.

It has been found highly desirable to provide means whereby the pitch change from feathering position through coarse and fine pitch positions to reverse pitch position also in the opposite direction maybe efiected at differing rates of speed as required by flight conditions. A partial step in the direction of accomplishing this desideratum is disclosed in the Archibald G. Forsyth application, S. N. 465,618, filed November 14.1942, which discloses booster'means which may be employed to speed up the pitch change in both directions over a limited range when flight conditions require. Thus, in accordance with that invention it is possible when required to speed up the pitch changing movement from fine pitch to reverse pitch'or from reverse pitch to fine.

The present invention renders it possible to effect such results through all pitch positions and by means of simplified mechanism, compactly arranged to meet the rigid space requirements of variable pitch propeller systems, particularly The principal object of the invention is to provide such an arrangement.

Another object of the invention is to-accomplish such difiering speed pitch changing movements through the same electric motor employed for the pitch changing movement without the necessity of employing auxiliary power means. These and further objects of the invention will become more apparent from the following description and claimswhen read in conjunction with the accompanying drawings in which:

Fig. 1 is a view ofone form of the invention, partially in section, the electric circuit being shown diagrammatically.

a this housing contains pitching mechanism including a gear, such as the ring gear 4, suitably geared or otherwise operably connected to rotate the propeller blades (not shown) about their longitudinal axes to vary their pitch.

The ring gear 4 is adapted to be rotated in one direction or the other by a worm 6 mounted on the shaft 8 mounted in bearings I0 carried by the housing 2.

The shaft l0 has two spaced gear wheels l2 and I4 normally freely rotatable thereon.

To accommodate the mechanism of the present invention, the housing 2 is provided with a supplemental housing 2'. The shaft extends into this supplemental housing 2' and the gear wheels l2 and M are also mounted therein.

Between the gear wheels 12 and i4 and keyed on shaft 8 is a sleeve Hi. This sleeve rotates with the shaft but is mounted for axial sliding movement on the shaft, which movement is effected by the'pivoted lever [8. The lower end of the lever I8 is bifurcated a shown in Fig. 2 and the arms 20 of the bifurcation are provided with inwardly projecting lugs 2| disposed in the annular groove 22 in the sleeve I6 so that movement of the lever in one direction or the other will slide the sleeve toward gear wheels I2 or M, respectively.

Gear wheels l2 and H have dogs 24 on their facing sides which dogs are adapted to be engaged respectively by dogs 26 carried by and rigid with the sleeve l6.

Gear wheel I2 is engaged by a gear 28 mounted for rotation within the supplemental housing 2'. Gear 28 is in turn engaged by a pinion 30 mounted within housing 2' and driven by a reversible electric motor 32 carried by housing 2'..

Gear wheel I4 is engaged by a gear 3, in turn engaged by a pinion 36 also driven by the electric motor. Advantageously, the pinions 30 and 36 may be integrally formed on a sleeve 3 8 suitably splined to the drive shaft of motor 32.

tion and operation of the electric motor 32 would not, therefore, transmit movement to the shaft 6 since gears I2 and I4 are freely rotatable on said shaft. However, if lever i8 is moved to the left in Fig. l, the dogs 26 on the sleeve i6 will engage the dogs 24 on the gear I2, and operation of motor 32 will then, through gears 36, 28 and I2, transmit rotary movement to the shaft 2, thus rotating worm and actuating the pitch changing gear 4 in either direction depending on the direction of rotation of the motor.

Conversely, when lever I8 is moved to the right, the dogs 26 on sleeve It will engage the dogs 26 on gear I and operation of motor 32 in one direction or the other will, through gearing 36, 34 and M, rotate shaft 8 and worm 6, thus effecting a pitch changing movement. Since, however, the gears in this gearing differ in size and arrangement from gearing 36, 28 and 82, it is obvious that the pitch changing movement in either direction effected therethrough will be at a lesser rate of speed.

As previously explained this is of considerable advantage because flight conditions frequently demand rapid changes from one pitch position to another.

In Fig. 1 an electric control circuit is diagrammatically shown. The motor 32 is connected in this circuit to be energized by the battery 40 when the circuit is closed. Also in the circuit, are the reverse, feathering, fine and coarse pitch limit switches 42, 44, 48 and 48 each adapted to be broken by the cams 50, 52, 54 and 56 respectively. These cams are driven by the motor 32 by any suitable means (not shown) and are for tripping the switches 42, 44, 46 and 48 when predetermined limits of reverse pitch, feathering pitch, fine and coarse pitch positions have been attained through operation of motor 32.

The control circuit also includes two switches 58 and 60 adapted respectively to be actuated by the arms 62, 64 carried by the upper portions of lever I8. Actuation of lever I8 in one direction or the other will consequently close the circuit to start the motor while simultaneously operatively connecting the shaft 8 to one set of gearing or the other.

When the lever I8 is moved to the right or to low gear position, switch 60 will be made or closed thus directing current to motor 32. Switches 46 and 46 are normally'made and pitch changing movement through low gearing 36, 34, and I4 will continue until either the fine position cam 54 or the coarse position cam 56 breaks its respective switch and shuts ofi the motor. The cams 54 and 56 are so designed that the pitch changing movement toward fine and coarse pitch will be stopped when predetermined fine pitch and coarse pitch limits have been reached.

The actuation of the motor 32 in one direction or the other between fine and coarse pitch positions may be controlled by governor means (not shown) but similar to those illustrated and described in the Archibald G. Forsyth application S. N. 449,123 to which reference has already been made.

When lever I8 is moved to the left to "high gear position, the arm 62 on lever I8 closes switch 58 in the circuit line including reverse and feathering pitch limit switches 42 and 44 which are normally closed. Depending on the direction of the motor 32, pitch changing movement toward reverse or feathering pitch positions will continue until either the reverse pitch cam 56 or the feathering pitch cam 52 will break its respective switch 42 or i l and thus shut off the motor.

The arrangement illustrated in. Figs. 3 and 4 is generally similar to that just described with one exception. This exception relates to the manner of actuating the sleeve it. In this instance, the end of shaft a is formed as a hollow cylinder 66 in which a piston 58 is disposed. The piston carries a transverse rod it which passes through slots F2 in the wall of the cylinder and through the sleeve It splined to the cylinder. The piston 68 is adapted to be moved axially in the cylinder 66 by means of a rod l4, the outer end of which is operatively connected to the lower end of lever it. The end of rod 74 has two lateralrings l5, and the lower end of lever i8 is bifurcated. The bifurcated portions 46 are disposed between the rings l5. Actuation of the lever in one direction or the other will consequently move the piston 68 and also the sleeve I6 causing the dogs thereon to engage the dogs on the gear wheels I2 and I4, respectively. Rotation of either of said gear Wheels may thus be transmitted to the shaft 8.

The embodiment of the invention illustrated in Fig. 5 operates on a slightly different principle. In this modification the end of shaft 6 carries two free wheels I2 and I4, the inner portions of which are splined to the shaft 8 while the outer peripheral portions are adapted, through free wheel arrangements 18 and 80, so that these outer portions may rotate freely in one direction on their inner portions. Rotation of the outer portions in the other direction, however, causes the outer portions to be temporarily locked to the inner portions. The free wheel arrangements of wheels I2 and I4 are designed to lock in opposite directions. Such free wheels are well known per se and any such arrangements may be employed.

The device operates as follows: Rotation of the motor 32 in one direction will, through gearing 30 and 28, rotate the outer portion of gear wheel I2, thus causing it to lock to the inner portion thereof through the free wheeling arrangement 18. The shaft 8 is thus rotated. No motion is transmitted to shaft 8 through gearing 36, 34 and I4 because the free wheeling arrangement is such as to permit the outer portion of' wheel I4 to rotate freely on its inner portion when the motor is running in this direction.

Conversely, when the motor 32 is rotating in the other direction, actuation of gears 36 and 34 will, through the free wheeling arrangement 80, lock the outer and inner portions of wheel I4, thus transmitting movement to shaft 8. During this time theouter portion of gear wheel I2 freely rotates on its inner portion as the free wheeling arrangement 18 is only adapted to lock when the outer portion of wheel I2 is rotating in the opposite direction.

It will thus be noted that pitch changing movement in one direction is carried out at a faster rate of speed than in the other. Thus a pitch change from feathering pitch position, through coarse and fine'pitch, to reverse pitch may be effected with high" gear (gearing 30, 28 and I2). while a pitch change in the other direction from reverse pitch, through fine and coarse to feathering, may be effected through low" gear gearing 36, 34 and I4). 4

As in the first embodiment, and also as disclosed in the Archibald G. Forsyth application, S. N. 449,123, referred to supra, limit switches controlled by cams driven by motor 32 may be used for shutting oil the motor when a predetermined pitch position has been attained.

Fig. 6 is similar to Fig. 5 but shows how a more pronounced speed ratio may be efiected by staggering the axes of the gear wheels 34 and 28.

The invention can 'be employed with various types of variable pitch propeller systems including those having two or more sets of propellers driven from coaxial propeller drive shafts. Moreover, because of its simplicity and the little space it requires, it is admirably suited for pitch control systems of the self-contained type such as shown, for example, in the Archibald G. Forsyth application, S. N. 472,882, filed January 19, 1943.

Manifestly, changes in structure, design and operation may be made within limits without departing from the invention. The modification illustrated and described is exemplary only and the scope of the invention is only to be limited as defined in the claims which follow.

We claim:

1. In a propeller system for aircraft and the like and having at least one set oi variable pitch propellers, means for driving the pitch changing mechanism of said propellers, said means comprising a reversible motor and gearing adapted to be driven by said motor to drive said pitch changing mechanism in one direction or the other, said gearing including two gear trains providing diil'ering gear ratios, and each gear train including mechanism which transmits driving movement in one direction only, and each of said mechanisms being disposed to transmit movement only in a direction opposite to the other.

2. In a device as defined in claim 1, said motor being electric, a circuit for said motor, and means driven by said motor for breaking said circuit to shut oil the motor when predetermined pitch positions have been reached. I

ARCHIBALD GRAHAM FORSYTH. GEORGE JAMES SMITH-PERT. 

